The present invention relates to a new and improved construction of an apparatus for brightening cockpit instruments.
In its more particular aspects, the present invention specifically relates to a new and improved construction of an apparatus for brightening cockpit instruments by means of daylight shining through front windows of the cockpit. A daylight throughpass opening is provided in a vizor arranged at an instrument panel containing the cockpit instruments. Optical deflection means are associated with the daylight throughpass opening for brightening cockpit instruments.
The cockpit of an aircraft is subjected to continuously changing light incidence directions and light intensities due to changing flight conditions. Various provisions have been taken for preventing exposure of the pilot to undesirable glare and reflections. It is for this reason that, for example, the cockpit is dark colored. The incidence of light or daylight into the cockpit is reduced such that thereby the outlook from the aircraft is optimized.
However, problems still result in reading the cockpit instruments during day-time. The viewer's or pilot's eye is adapted to the high brightness of the daylight incident through the front window of the cockpit. Reading of the instruments is rendered difficult due to the brightness difference between the field of view defined by the front window and the dark cockpit.
The night-time illumination installed in the instrument panel containing the cockpit instruments is designed for dark-adapted eyes. Such night-time illumination can hardly contribute to improving the readability of the cockpit instruments during day-time. Increasing the intensity of the "active" night-time illumination of the cockpit instruments would have the undesirable effects of additional power requirements, additional heat generation as well as added and heavier wiring resulting in additional weight.
In an instrument lighting apparatus used in connection with, for instance, aircraft and as known, for example, from German Published Patent Application No. 2,944,537, published May 22, 1980, there are present, in addition to an internal light source, means for directing daylight to the instruments. For this purpose, there is provided a light guide which extends through an upper upholstery or a glare protection towards the front window and which has an edge surface through which incident daylight is passed into the light guide. The light guide is constructed as a plate extending on the rear side of the scale-carrying member as seen by the viewer. The light guide has a rear side which is remote from the scale-carrying members of the instrument panel and constitutes a reflecting surface. The light guide has a front side which faces the scale-carrying members of the instrument panel and constitutes a light emitting surface emitting the incident deflected day-light. In this arrangement the incident daylight thus is passed to the rear of the instrument panel remote from the side facing the viewer and the desired brightening is caused by the daylight which is transmitted or throughpassed through the scale-carrying members. A similar device has been disclosed in U.K. Patent application GB 2,056,740 A, published Mar. 18, 1981.
German Utility Model No. 1,955,159, granted Dec. 14, 1966, is directed to a device for indirectly illuminating the scale of measuring instruments. In this device, the light which is emitted by a light source located on the rear of a scale as seen by the viewer, is passed through a light guide and a bent-off portion of a cover plate to a total-reflecting layer wherefrom the light is shined upon the front surface of the scale. There are no means provided for using daylight in this device to brighten the scale. A similar device is known from European Patent application 0,088,281 A1, published Sep. 14, 1983.
A publication entitled "Light-Valve Display" in the Journal "Neues aus der Technik", issue no. 4, page 4, dated Dec. 15, 1988, is concerned with an arrangement in which diffuse light originating from a concave mirror is throughpassed through parallel slots of a shutter and a facetted grating facing the viewer. The inactive facets of the grating are blackened in order to minimize internal and external reflections and the formation of double images.
German Patent No. 739,720, issued Oct. 2, 1943, relates to a synthetic glass plate covering an instrument panel. The synthetic glass is opaque on the viewer's side and contains cut-outs in the region of the instruments. A light source is inserted into the synthetic glass plate for shining diffuse light upon the instruments.
German Published Patent Application No. 3,245,299, published Jun. 14, 1984, relates to indicator means in a motor vehicle, particularly a dashboard provided with electronic brightness control means associated with the indicating elements. Additionally, there are provided photodetectors which respectively respond to the daylight impinging upon the instrument panel and the daylight entering the interior of the motor vehicle through the front window. The photodetectors are connected to the electronic brightness control means whereby the same is made dependent upon the incident daylight.
U.S. Pat. No. 2,695,354, granted Nov. 23, 1954, is concerned with instrument panel lighting in an aircraft using glare-free indirect illumination by means of a synthetic glass plate.
U.S. Pat. No. 2,375,134 relates to a mirror globe arranged in an aircraft pilot's field of view. A plural number of further mirrors which are placed at the aircraft, are aligned to the mirror globe. The pilot is thereby enabled to observe various parts of the aircraft and their environment.